This article covers the configuration needed to turn on power saving features. Almost all of the features listed here are worth using whether or not the computer is on AC or battery power. Most have negligible performance impact and are just not enabled by default because of commonly broken hardware/drivers. Reducing power usage means reducing heat, which can even lead to higher performance on a modern Intel or AMD CPU, thanks to [[Wikipedia:Intel Turbo Boost|dynamic overclocking]].

This article covers the configuration needed to turn on power saving features. Almost all of the features listed here are worth using whether or not the computer is on AC or battery power. Most have negligible performance impact and are just not enabled by default because of commonly broken hardware/drivers. Reducing power usage means reducing heat, which can even lead to higher performance on a modern Intel or AMD CPU, thanks to [[Wikipedia:Intel Turbo Boost|dynamic overclocking]].

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== Ready to run scripts ==

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== Configuration ==

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There are already a couple of scripts and tools which make use of the various settings described in the next section. These are notably:

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* [[TLP]]

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* [[Powerdown]]

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* {{AUR|powerconf}}

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*{{AUR|ftw-git}}

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* [[Laptop Mode Tools]]

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* [[pm-utils]]

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If you do not want to take care of the settings by yourself it is recommended to use these tools. But be aware of running only '''one''' of these tools to avoid possible conflicts as they all work more or less similar.

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== Custom settings ==

If you would like to create your own scripts and power saving settings such as by udev rules you can take the following settings as a reference.

If you would like to create your own scripts and power saving settings such as by udev rules you can take the following settings as a reference.

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=== Audio ===

=== Audio ===

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By default, audio power saving is turned off by most drivers. It can be enabled by setting the power_save parameter to a time (in seconds) to go in idle.

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By default, audio power saving is turned off by most drivers. It can be enabled by setting the {{ic|power_save}} parameter; a time (in seconds) to go into idle mode. To idle the audio card after one second, create

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{{Note|Toggling the audio card's power state can cause a popping sound or noticeable latency on some broken hardware.}}

Either {{ic|[default]}} or {{ic|[powersave]}} means you do not need to force it on.

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Either {{ic|[default]}} or {{ic|[powersave]}} means you do not need to force it on. Otherwise, it's either unsupported or broken on your hardware, or has to be forced on with {{ic|1=pcie_aspm=force}} on the [[kernel line]].

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Otherwise, it's either unsupported/broken on your hardware, or has to be forced on with {{ic|1=pcie_aspm=force}} on the [[kernel line]].

If you won't use integrated web camera then [[Kernel_modules#Blacklisting|blacklist]] the {{ic|uvcvideo}} module.

If you won't use integrated web camera then [[Kernel_modules#Blacklisting|blacklist]] the {{ic|uvcvideo}} module.

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=== Disabling NMI watchdog ===

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=== Kernel parameters ===

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This section uses configs in {{ic|/etc/sysctl.d/}}, which is ''"a drop-in directory for kernel sysctl parameters, extending what you can already do with /etc/sysctl.conf."'' See [http://0pointer.de/blog/projects/the-new-configuration-files The New Configuration Files] and more specifically [http://0pointer.de/public/systemd-man/sysctl.d.html systemd's sysctl.d man page] for more information.

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==== Disabling NMI watchdog ====

The [[Wikipedia:Non-maskable interrupt|NMI]] watchdog is a debugging feature to catch hardware hangs and cause a kernel panic. On some systems it can generate a lot of interrupts, causing a noticeable increase in power usage.

The [[Wikipedia:Non-maskable interrupt|NMI]] watchdog is a debugging feature to catch hardware hangs and cause a kernel panic. On some systems it can generate a lot of interrupts, causing a noticeable increase in power usage.

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{{hc|/etc/sysctl.d/disable_watchdog.conf|2=kernel.nmi_watchdog = 0}}

{{hc|/etc/sysctl.d/disable_watchdog.conf|2=kernel.nmi_watchdog = 0}}

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or add {{ic|1=nmi_watchdog=0}} as a [[kernel parameter]] to disable it completely from early boot.

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or add {{ic|1=nmi_watchdog=0}} to the [[kernel parameter|kernel line]] to disable it completely from early boot.

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=== Disabling Wake-on-LAN ===

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==== Writeback Time ====

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Increasing the VM dirty writeback time can help to aggregate I/O together - reducing disk writes, and decreasing power usage:

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[[Wikipedia:Wake-on-LAN|Wake-on-LAN]] can be a useful feature, but if you're not making use of it then it's simply draining extra power waiting for a magic packet while in suspend.

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vm.dirty_writeback_centisecs = 1500

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Disabling for all Ethernet interfaces:

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To do the same for journal commits with ext4 and some other filesystems, use {{ic|1=commit=15}} as a parameter in [[fstab]] or with the {{ic|rootflags}} [[kernel parameter]].

[[Wikipedia:Wake-on-LAN|Wake-on-LAN]] can be a useful feature, but if you're not making use of it then it's simply draining extra power waiting for a magic packet while in suspend. Disabling for all Ethernet interfaces:

{{Note|This should be combined with [[udev#Network device|static naming]] of devices, the eth* names are not static. In the below examples there are some assumptions about how your devices are named. The first assumes that your wireless has the kernel name of "wifi0" and the second that any wireless interface will begin with "wlan". Of course, with persistent naming included now in systemd, this is probably no longer the case. "%k" in the second example is a variable for the kernel name for the matched device. For example if it finds that the rule is applicable to wlan1, the "%k" variable will be replaced ith "wlan1".}}

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In these examples, {{ic|%k}} is a specifier for the kernel name of the matched device. For example, if it finds that the rule is applicable to {{ic|wlan0}}, the {{ic|%k}} specifier will be replaced with {{ic|wlan0}}. To apply the rules to only a particular interface, just replace the pattern {{ic|eth*}} and specifier {{ic|%k}} with the desired interface name. For more information, see [http://www.reactivated.net/writing_udev_rules.html Writing udev rules].

In this case, the name of the configuration file is important. Due to the introduction of [[Network_Configuration#Device_names|persistent device names]] via {{ic|80-net-name-slot.rules}} in systemd v197, it is important that the network powersave rules are named lexicographically before {{ic|80-net-name-slot.rules}}, so that they are applied before the devices are named e.g. {{ic|enp2s0}}.

There are many scripts and tools which make use of the various settings described in the previous sections. These are notably:

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* [[TLP]]

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* [[Powerdown]]

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* {{AUR|powerconf}}

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* {{AUR|ftw-git}}

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* [[Laptop Mode Tools]]

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* [[pm-utils]]

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If you do not want to take care of the settings by yourself it is recommended to use these tools. But be aware of running only '''one''' of these tools to avoid possible conflicts as they all work more or less similar.

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{{Tip|Have a look at the [[:Category:Power management|power management category]] to get an overview on what power management options exists in Archlinux.}}

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=== Using a script and an udev rule ===

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Since systemd users can suspend and hibernate through {{ic|systemctl suspend}} or {{ic|systemctl hibernate}} and handle acpi events with {{ic|/etc/systemd/logind.conf}}, it might be interesting to remove pm-utils and acpid. Now, there's just one thing systemd can't do (at this time of writing): powermanagement, depending on whether the system is running on AC or battery. To fill this gap, one can create a single udev rule that launches a script when the laptop is unplugged and plugged:

{{Note|One can use the same script that pm-powersave uses. You just have to make it executable and place it somewhere else (for example, /usr/bin).}}

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Examples of powersave scripts can be found here: [https://bbs.archlinux.org/viewtopic.php?pid=1046075#p1046075] (or in aur: {{AUR|powerdown}}), here: [https://github.com/Unia/powersave] and there: [https://aur.archlinux.org/packages/powerconf].

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The above udev rule should work as expected, but if your power settings aren't updated after a suspend or hibernate cycle, you should add a script in {{ic|/usr/lib/systemd/system-sleep/}} with the following contents:

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{{hc|/usr/lib/systemd/system-sleep/00powersave|<nowiki>

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#!/bin/sh

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case $1 in

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pre) /path/to/your/script false ;;

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post)

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if cat /sys/class/power_supply/AC0/online | grep 0 > /dev/null 2>&1

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then

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/path/to/your/script true

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else

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/path/to/your/script false

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fi

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;;

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esac'

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exit 0

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</nowiki>}}

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Don't forget to make it executable!

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{{Note|Be aware that AC0 may be different for your laptop, change it if that is the case.}}

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Now you don't need pm-utils anymore. Depending on your configuration, it may be a dependency of some other package. If you wish to remove it anyway, run {{ic|pacman -Rdd pm-utils}}.

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=== Print power settings ===

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This script prints power settings and a variety of other properties for USB and PCI devices. Note that root permissions are needed to see all settings.

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{{bc|<nowiki>#!/bin/bash

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for i in $(find /sys/devices -name "bMaxPower")

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do

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busdir=${i%/*}

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busnum=$(<$busdir/busnum)

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devnum=$(<$busdir/devnum)

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title=$(lsusb -s $busnum:$devnum)

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printf "\n\n+++ %s\n -%s\n" "$title" "$busdir"

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This function shows various power settings. Note you either must be root or you must have sudo.

Configuration

If you would like to create your own scripts and power saving settings such as by udev rules you can take the following settings as a reference.

Audio

By default, audio power saving is turned off by most drivers. It can be enabled by setting the power_save parameter; a time (in seconds) to go into idle mode. To idle the audio card after one second, create

/etc/modprobe.d/audio_powersave.conf

options snd_hda_intel power_save=1

for Intel, or use

options snd_ac97_codec power_save=1

for ac97.

Note: Toggling the audio card's power state can cause a popping sound or noticeable latency on some broken hardware.

In these examples, %k is a specifier for the kernel name of the matched device. For example, if it finds that the rule is applicable to wlan0, the %k specifier will be replaced with wlan0. To apply the rules to only a particular interface, just replace the pattern eth* and specifier %k with the desired interface name. For more information, see Writing udev rules.

In this case, the name of the configuration file is important. Due to the introduction of persistent device names via 80-net-name-slot.rules in systemd v197, it is important that the network powersave rules are named lexicographically before 80-net-name-slot.rules, so that they are applied before the devices are named e.g. enp2s0.

PCI Runtime Power Management

/etc/udev/rules.d/pci_pm.rules

ACTION=="add", SUBSYSTEM=="pci", ATTR{power/control}="auto"

SATA Active Link Power Management

Note: This adds latency when accessing a drive that has been idle, so it's one of the few settings that may be worth toggling based on whether you're on AC power.

Tools and scripts

Packages

If you do not want to take care of the settings by yourself it is recommended to use these tools. But be aware of running only one of these tools to avoid possible conflicts as they all work more or less similar.

Using a script and an udev rule

Since systemd users can suspend and hibernate through systemctl suspend or systemctl hibernate and handle acpi events with /etc/systemd/logind.conf, it might be interesting to remove pm-utils and acpid. Now, there's just one thing systemd can't do (at this time of writing): powermanagement, depending on whether the system is running on AC or battery. To fill this gap, one can create a single udev rule that launches a script when the laptop is unplugged and plugged:

Note: One can use the same script that pm-powersave uses. You just have to make it executable and place it somewhere else (for example, /usr/bin).

Examples of powersave scripts can be found here: [1] (or in aur: powerdownAUR), here: [2] and there: [3].

The above udev rule should work as expected, but if your power settings aren't updated after a suspend or hibernate cycle, you should add a script in /usr/lib/systemd/system-sleep/ with the following contents: